INTERVAL キーワードで設定されたクローズドユニット値を使用すると、MySQL は何を返しますか?

mysql> Select TIMESTAMP('2017-10-22 04:05:36' + INTERVAL '4 2' Hour)AS 'HOUR VALUE INCREASED BY 4';
+---------------------------+
| HOUR VALUE INCREASED BY 4 |
+---------------------------+
| 2017-10-22 08:05:36       |
+---------------------------+
1 row in set, 1 warning (0.00 sec)

mysql> Show warnings;
+---------+------+------------------------------------------+
| Level   | Code | Message                                  |
+---------+------+------------------------------------------+
| Warning | 1292 | Truncated incorrect INTEGER value: '4 2' |
+---------+------+------------------------------------------+
1 row in set (0.00 sec)